iWatch still grossly inaccurate on distance

The Apple Series 5 is a GPS watch. In my case I paid extra for the GPS + Cellular version so it should have connectivity with or without WiFi. I wanted something with reliable accuracy. In addition I always carry my iPhone on my walks paired to the watch. I learned early on that the watch by itself is less accurate without the iPhone.

Apple support confirmed every setting during the diagnostic testing we did. But they have been consistently the same settings over the same pre-measured course. I have recalibrated and done every other software tweek that I could find.

The watch worked pretty well for months until a software update which, after it was applied overnight, the watch has never been the same from the next day. Apple support and engineering does not appear to know the reason, or they know and will not admit the issue. I worked in software support for sixteen years and have done troubleshooting on systems so this is not my first rodeo in this general area. I suspect there was some change in the update that affected the accuracy. I think Apple should be more diligent and provide premium products and support to match their premium pricing.

I use a measured course. The actual distance was 3.25 miles. The Activity Tracker app on my phone was close. The third party app people at Activity Tracker say it uses the same Apple motion sensor as the watch. This is a route which I have used over the last 2 years since March 2020. I walk every day. The watch measured approximately the same distance as the app and the expected actual distances until the software update referenced before. Problems occurred immediately after updates to version of iOS (15.1) on my iPhone and watch version (8.1) and have not been accurate since then.

I recently recalibrated my watch. But today is a new low in accuracy. The workout reports 2.78 miles while the Activity Tracker app says 3.3 miles. That implies an error of 18% on what is supposed to be a GPS based device. That is awful.

I use a measured course. The actual distance was 3.25 miles. The Activity Tracker app on my iPhone was close. The third party app people at Activity Tracker say it uses the same Apple motion sensor as the watch. This is a route which I have used over the last 2 years since March 2020. I walk every day. The watch measured approximately the same distance as the app and the expected actual distances until the software update referenced before. Problems occurred immediately after updates to version of iOS (15.1) on my iPhone and watch version (8.1) and the metrics have not been accurate since then. I have also used pedometers. I offer the app has a point of comparison and realize none of the devices will be 100 per cent accurate. But GPS devices should be within an expected error range and even Apple support has said it is outside the expected tolerance. I have asked for another watch but Apple support did not even respond to that request. No reason for the errors have been forthcoming and no updates on the bug report since December. I am disappointed to say the least.

Nothing about the GPS signal should have changed overnight. The update seems to be the 'culprit' as it was the one change that appeared to result in the problems. The steps in the link that you sent have all been done repeatedly both on my own and with the help of Apple Support. Apple Support downloaded and ran diagnostic software and did a bug report.

Problems occurred immediately after updates to version of iOS (15.1) on my iPhone and watch version (8.1).

Yes I am up to date. I update every time a new one becomes available. I stay up to date in hopes that Apple will resolve the issues and correct these problems.